400 main cap - Team Camaro Tech
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post #1 of 3 (permalink) Old Mar 6th, 03, 08:48 PM Thread Starter
Tech Team
Join Date: Aug 2001
Location: Eugene, OR, USA
Posts: 77

Hey I was just installing the oil pump on my rear main cap by torquing it down and all of a sudden the hole for the bolt cracks around the top and breaks off down a few threads, looking like a crater around the hole for the bolt. I was wondering where I could get a just a rear main cap or do I have to order all of them. Also I paired up my 350 main cap, though it looks the same, the lower bearing doesn't fit. Is there supposed to be a difference? Any suggestions to remedy the problem.
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post #2 of 3 (permalink) Old Mar 6th, 03, 09:19 PM
Senior Tech
Join Date: Feb 2002
Location: N.W. Washington
Posts: 7,964

ouch! that sucks, yes the main journal of a 400 is larger than a 350, so it has to be a 400 cap. i don't really know if you can buy new factory caps or not, i believe you could get an aftermaket steel cap, but thats probably not the answer. my guess is wrecking yard or possibly a machine shop might have spares. but, to do this right, you should at least get the mainline of the block and new bearing checked, it may (probably) will need to be align honed. also, i would first try to figure out why the cap broke in the first place. was the bolt not deep enough into the threads? sorry to hear it, probably no easy fix, at least not a reliable one. good luck!
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post #3 of 3 (permalink) Old Mar 6th, 03, 09:30 PM
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Join Date: Jan 2002
Location: Calgary, Canada
Posts: 1,860

Are there still some threads in the cap?, or did just the top 2 break off? This usually occurs when the oil pump bolt is to short. If you still have 4 or 5 threads you could just put a ARP oil pump stud in the cap and it probably will work OK. If possible try to save it as another cap has to be either align bored or honed, and a lot of times the thrust will be off , causing more grief, although you can drill the main cap bolt holes 1 drill size over stock and move the cap around before torquing it to specs. Make sure you red loctite the stud in and be carefull not to install it too deep as some 400 rear caps are drill through to the brg. Hope this helps.
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